Wireless Help - Why doesn't my laptops connect via 802.11n?

[ComputerBox34]

Background:

Have this device:
http://www.dlink.com/products/?pid=DAP-1522

Claims that it has 802.11n connectivity as well as b, g, etc.

Here is my configuration page as it stands right now:

Question:
How come none of my wireless N devices can connect using wireless N? Even if I set the access point to 5 ghz/wireless N only, my laptop still will not connect. The max speeds I get when I connect via 2.4 ghz is just 54 mb/s which is just 802.11g.

Any ideas? Would really like to get this working since a majority of the laptops on my network try streaming HD content but have trouble doing so with the lower speeds.

 

[moetop]

TKIP. you need AES

Also good reading
http://www.smallnetbuilder.com/wireless/wireless-basics/30664-5-ways-to-fix-slow-80211n-speed Although I do not necessarily agree with #5 in this one)

http://www.smallnetbuilder.com/wireless/wireless-basics/31083-smallnetbuilders-wireless-faq-the-essentials

http://www.smallnetbuilder.com/wireless/wireless-features/30938-dont-mess-with-wmm

 

[ComputerBox34]

Ah...thank you!

So the first thing I tried was to run it as a hybrid: 2.4 ghz with N and G as well as TKIP and AES....didn't work out too well.

Since I have 2 other access points in my house that are G, I made this N only with the AES encryption. Now riddle me this:

Some of my N laptops connect fine without a problem and get amazing speeds. (I had to manually go in and change the cipher type first, no problems after that) But some of my other laptops don't even see the network anymore...it's just gone. I manually changed the cipher in the Windows 7 properties but I still can't see the network, let alone connect.

Edit: After doing some research, it looks like some of these wireless cards are meant to be "power saving" or whatever and are capped at 150 mb/s rather than 300. Is this because they are only looking on the 2.4 ghz band and can't see the 5?

 

[InvisiBill]

http://en.wikipedia.org/wiki/802.11n#Number_of_antennas
802.11n can do a max of 150Mbps per spatial stream, and each spatial stream requires a physical antenna (in addition to any limits on the radio itself). If a cheap adapter only has a single Tx antenna, it's simply impossible for it to go faster than 150Mbps. Also, 20MHz channels will basically cut your speeds in half. Using 40MHz channels on 2.4GHz requires a huge amount of the available spectrum (up to 82% of it), and is often not very feasible.